Screening machine and screen cloth therefor



B. MITCHELLV SCREENING MACHINE AND SCREEN CLOTH THEREFOR Filed Sept. 301920 3 Sheets-Shea?, l

z C /Ca i Jun@ 26, E923. L45945 B. A. MITCHELL SCREENING MACHINE ANDSCREEN CLOTH THEREFOR Filed Sept. 30 1920 v3 Sheets-Sheet 2 Jun@ Z6,11923. l

B. A. MHTGHEILL SCREENING MACHINE AND SCREEN CLOTH THEREFOR Filed Sept.30 1920 3 Shwtcsheeb 5 to the heavy wires on screen cloth for usePatented June 26, 1923.

UNITE-D STATES PATENT QFFICE.

BENJAMIN A. MITCHELL, OFGARFIELD, UTAH.

SCREENING MACHINE AND SCREEN CLOTH THEREFOB.

Application led September 30, 1920. Serial No. 418,843.

To all whom zit may concern.'

Be it known that I, BENJAMIN A. MITCH- ELL, a citizen of the UnitedStates, residing at Garlield, in the State of Utah, have inventedcertain new and useful Improvements in Screening Machines and Screen,Cloth Therefor, of which the following is a` speciication. v

This invention relates to improvements in in screening machines and toimprovements in such machines fox` screening finely divided or crushedmaterials.

The

principal Vobject of the invention is to provlde an improved screencloth havingv or heavy wlres interwoven relatively large with thecomparatively fine wires which compose the body portion of the screen.Another object of the invention is to provide a woven wire' screen clothreinforced with heavy wires, in which the dimensions of the meshes ofthe cloth, transversely to the heavy wires, are substantially uniformthroughout the screen. Still another object is to provide a Woven wirescreen cloth having relatively large wires of approximately ellipticalor oblong cross section interwoven with the fine wires of the screen.Other objects relate to various features of construction and arrangementsuch as will be more fully pointed out hereinafter.

The nature of the invention will be understood from the followingspecification taken in connection with the accompanying drawings, inwhich certain embodiments are illustrated.

In the drawings-` Fig. 1 shows a top plan view of the improved screencloth;

Fig. 2 shows a sectional view transversely Fig. 3shows a longitudinalsectional view on the line 3 3 of Fig. 4, illustrating one method ofconnecting the screen cloth to the screening machine;

Fig. 4 shows a top plan view of a screening machine with the improvedscreen cloth embodied therein;

Fig. 5 4is a perspective view of the machine-illustrated in Fig. 4looking toward the underside thereof;

Fig. 6 shows-a side elevation of the screening machine with a feedingdevice shown in vertical section;

Fig. 7 shows an enlarged vertical section throughthe screen clothtransversely t0 the ffound that, by

the line 2-2 of Fig. 1;'

of the vlbrations which may screen cloth; y

The form of screen cloth illustrated particularly in Figs. 1 and 2comprises a plurality of longitudinal weft wires 15 which are interwovenwith a plurality of transversely extending warp wires 16'. The wires l5and 16 are comparatively small in cross section and the wires 15 havesubstituted therefor, at predetermined intervals, the comparativelylarge weft wires 17 which are preferably oblong or approximatelyelliptical in cross section, as illustrated in Fig. 2. The ne wiresl 15and 16 are spaced equal distances aparty to form meshes 18, which aresubstantially rectangular and it has been employing heavy wires 17 ofoblong cross section, it is possible t6 maintain the meshes 18 uniformin size throughout .the width of the screen cloth. If the heavy wires'17were circular in cross section and of a diameter equal to the shorterdimensions of these wlres, as illustrated in Fig. 2, it will be apparentthat the meshes 18a on each side of each heavy wire would havedimensions transversely to the heavy wires greater than thecorresponding meshes formed by the interwoven fine wires. The use of aheavy wire having an oblong cross section overcomesthis difficulty, dueto the fact that the projecting lateral edges of the heavy wirespartially fill the meshes so that the openings 18a adjacent the heavywires can be maintained the same in size as any e set up in the p ,ofthe other meshes formed by the fine wires v alone.

The screen cloth thus formed is particularly adapted for use inscreening meshes for screening orV separating crushed ore, sand, gravel,or other similar materials which are caused to pass over the screencloth, preferably while it is being vibrated. lhe heavy wires give anincreased stiffness to the screen cloth and are adapted to increase theetliciency of the vibratlons therein and, while at the same time, theprovision of a uniform size of mesh makes it possible to maintain auniform ineness "of the screened material.

Th application to a screening machine of screen cloth made in.accordance with this Ainvention. The machine here shown comprises aframe 2O having a centrally located cross frame member 2l united at itsends with upwardly extending arms 22. These memere is illustrated inFigs. 4, 5 and 6 anY heavy wires thereof, showing the character loo4 gianges 23". has relatively large or bers 22 are flared outwardly attheir upper ends and terminate in the end frames 23 of angular crosssection having upwardly extending ilanges 23a and inwardly directed Thescreen cloth shownr at 25 heavy wires 25? interwoven thereinl extendinglongitudinally thereof, Aand is mounted between the end frame members 23the screen being secured thereto-by means of pairs of clamping bars 26.These clamping bars are placed on opposite sides ofthe screen cloth Aandare secured together by bolts 27 so that the bars 26 are caused to gripfirmly the heavy wires 25a of the screen cloth. The lower 'bar 26 ofeach '(pair has a number of` longitudinally exten ing bolts 28 weldedthereon, or otherwise secured thereto, and these` bolts are adapted toengage the notches 29 which are formed in the end frame members 23. Thethreaded extremities of the bolts 28 are engaged b nuts 30 so that atension can be created 1n the screen cloth longitudinally of the heavywires 25.

The screen frame 20, as illustrated in Fig. 6, is stationarily supportedin screening position with the screen cloth preferably in van inclinedposition. The upper extremities o the end frame members 23 arelongitudinally extending pins 32 'adapted to engage the brackets 33carried by the vertical wall 34. On their lower extremities, the endframe members 23 are provided with cylindrical rejections or bosses `35which are threade ly engaged by vertically extending adjusting members36. These adjusting members engage plates 37 secured to the upper edgeof a vertical supporting wall 38 and, by regulating the members 36, itis possible to vary the inclination of the screen frame and t ecorresponding inclinations of the screen cloth carried thereby. Theadjusting members 36 ane secured in adjustedv position by means of locknuts 39. The material to be screened is delivered from a hopper 40 fromwhich -it passes onto a rotary drum conveyor 41 and an auxiliary hoppler42 onto the upper e e of the screen clot as illustrated at 43.

The material to be screened' passes downwardly b gravity over theinclined screen cloth, an is. subjected to the action of high fr uencevvlbrations set. up in the screen clot by means of the vibrator 45, whichprefers. ly is of the type disclosed in my copending applicatiom `SerialNo. 275,321,

utllizing the principle of rotating moments to produce a high frequencyharmonic motion or vibration 1n planes transverse to the pointsubstantiallyemidway of the longitu-'y axis of symmetry. f p Y Thevibrator 45 is shown as mounted at a dinal frame mein r 21, the vibratorbeing held inv position by means of the strap 65 which extendsy aroundits casing and is pro- ,nstance shown is in llarly in Fig. 5. providedwith.

is distributed thereby fromthreaded bars 67 are engaged by nuts 68 whichmay be adjusted to regulate the pressure with which the vibrator is heldin position on the frame. The mounting for the vibrator 45 is preferablya single point support under its centre of gravity which in the thecentral part thereof. This mounti l would preferably comprise asupporting co on the, frame 20 which engages with a coacting member onthe 4vibrator casing to rovide a pivotal support which, would ordsubstantially universal movement though limited of the casing whenexecuting vibration. Compressed air may be used to cool this apparatus.To this end it is shown as provided witI an aperture 72 where air may beintroduced and circulated through the frame 20 and thence up into thevibrator casing.

I The vibrations executed by the projecting ends of the vibrator 45 areimparted to the screen cloth by means of transmitting plates 75 whichare of the form illustrated particu- These plates are provided `withapertures which are adapted to be closely fitted by the taperedextremities 76 of the vibrator casinand the plates are held in positionon the v1 rator casin by means of keys 77 extending transverse y throughapertures formed in the projecting end flanges 78. The upper edges ofthe plates 75 liave lstrips 80 ofwood, or the like, secured -thereto andada ed to en ge the under side of the screen c oth-25. he upper edge ofeach plate 75 is preferably somewhat angular in contour, as shown 1nFig. 5, and the stri s 80 are arranged at corresponding ang es toconform to the inclination of the screen cloth` which is preferablyformed 'in two sections haiti different inclinations to the horizontalso t at the finely divided materials passing downwardly over the screencloth are retarded as the lower edge of the screen is approached. Thetransmitting plates' 7 5, extending upwardly from the vibrator, areadapted to transmit the circular vibrations from the casing ofthevibrator 45 to the screen cloth so that high frequency vibrations areset up in thescreen cloth in planes parallel to the paths of travel ofthe materials'being screened and transversely to the direction 1n whichthe heavy wires 25a extend. In practice, the vibrator is preferablylocated in such a direction thatv each particle of the screen cloth witravel 4teiwardthe upper edge of the scr en when in the upper part ofits ath of vibration. The vibrator 45 is preferably so constructed that,in operation the ends'of its-*casing execute vibrations which aresubstantially out of phase by 180 degrees, so that it beha/Ves sublarhaving a spherical surface stantially like a double conical pendulumvibrating. The vibrations are not necessarily circles, but they areharmonic vibrations having closed orbits, and a constantly changingdirection of motion. With the arrangement described, each particle ofthe screen cloth is caused to travel in a minute closed path, asillustrated by the arrows 88 in Fig. 7 of the drawin where thelongitudinal heavy wires 25u have a plurality of longitudinal fine wires25b arranged between them. Both the heavy wires 25a and the fine wires25" are interwoven with the transverse fine wires 25.

Instead of mounting the screen cloth in a frame, as shown in Figs. 4 and5, the vibrator 90 maybe secured to a xed frame member 91 by means of astrap 92, as shown in Fig. 12, with the free ends of the vibratorprojecting on opposite-sides of the frame and carrying the transmittingplates 93 secured thereto in the manner heretofore described. Thetransmitting plates 93 are engaged by the adjusting bolts 94 which aresecured to clamping members 95 attached to the screen cloth 96. Thescreen cloth' is thus supported by the transmitting plates 93, and thebolts 94 may be adjusted to create a tension in the screen cloth if atension is` desired.

Although I `have shown and described certain forms of the invention forpurposes of illustration, it will be understood that it ma beconstructed in various ways without departing from the scope of theappended claims.

I claim:

1. A Wire screen cloth adapted to be vibrated in screening machinescomprising a warp and weft of relatively line wires, said ne wires beingreplaced-at predetermined intervals with relatlvely heavy wires havingan oblong cross-section whereby a reinforced screen cloth havingsubstantially uniform mesh throughout is provided.

2. A wire screen cloth adapted to be vi-' brated in screening machinescomprising a warp and weft of relatively fine wires, said screen adaptedto be supported in a state of tension and having the fine wiresextending inthe direction of tension replaced at predetermined intervalswith relatively heavy wires having an oblong cross-section.

3.' A wire screen cloth adapted to be vibrated in screening machinescomprising a warp and weft of relatively line wires, said screen adaptedto be supported from two edges longitudinally displaced and having hefine wires extending longitudinally replaced at predetermined intervalswith relatively heavy wires having an oblong crosssection. A

4. A wire screen cloth adapted to be vibrated in screening machinescomprising a warp and weft of relatively fine Wires, Said screen clothhaving relatively large wires interwoven therein at vals and formed witha cross-section yielding substantially uniform mesh in directionstransverse thereto.

5. A wire screen cloth adapted to be vibrated in screening machinescomprising a warp and weft of relatively fine wires, said screen clothhaving relatively large wires interwoven therein at predeterminedintervals formed with approximately elliptical cross-sections. 6. A wirescreen cloth adapted `to be vibrated in screening machines comprising awarp and weft of relatively fine wires, said screen cloth havingrelatively"large wires interwoven therein at predetermined intervalsformed with approximately elliptical cross-section having its greaterdimension lying in the plane of the screen cloth.

1, wire screen cloth adapted to be vibrated in screening machinescomprising a warp and weft of relatively fine wires, said screen adaptedto be supported in a state of tension having the fine wire extending inthe direction of tension replaced at predetermined intervals withrelatively heavy Wires formed with approximately ellipticalcrosssections and arranged to have their greater dimension lie cloth.

8. In a screening machine, the combinain the plane of the screen y tionwith a vibrator, of a screen cloth reinwith interwoven relaadapted tosustain diof the received vibrations,

forced at intervals tively heavy wires rectly the stress saidreinforcing altered whereby to produce a cloth of substantially uniformmesh, and means for imparting motion from said vibrator to said screen.

9. In a screening machine, the combination with a vibrator, of a screencloth reinforced at intervals with interwoven relatively heavy wiresadapted to sustain directly the stress of the received vibrations, saidreinforcing wires having an'approximately elliptical cross-sectiommeansfor retainngsaid screen under tension, and means for imparting motionfromsaid vibrator to said screen.

10. In a screening machine, the combination with a vibrator, of a screencloth ,reinforced at intervals with 'interwoven relatively heavy wiresadapted to sustain directly the stress of the received vibrations, saidreinforcing wires having an approximately elliptical cross-section,means for stationarily supporting said screen, means for retaining saidscreen under tension, and 'means for imparting motion from said vibratorto said screen.

In testimony whereof, my name. f

BENJAMIN A. MITCHELL.

I have subscribed predeterminedy interv wires having a cross-section

